1. Technical Field
The present invention relates to an optical scanner, an image display device, a head mount display, and a heads-up display.
2. Related Art
An optical scanner for performing drawing by optical scanning has been used in a laser printer or an image display device. JP-A-2009-75587 discloses an optical scanner including torsion bar springs in two directions which are orthogonal to each other. According to this, in the optical scanner, a movable plate is oscillatably supported by a pair of first torsion bar springs. The other end of the first torsion bar spring is connected to a frame-shaped displacement portion. In addition, the displacement portion is oscillatably supported by a second torsion bar spring. The other end of the second torsion bar spring is connected by a frame-shaped support portion. A direction in which the first torsion bar spring extends is set as a first direction, and a direction in which the second torsion bar spring extends is set as a second direction. The first direction and the second direction are orthogonal to each other. Accordingly, the movable plate can be oscillated by using the two directions orthogonal to each other as rotation axes.
A permanent magnet is provided to surround the movable plate and the displacement portion in a plan view seen from a thickness direction of the movable plate. The permanent magnet is installed to be inclined by 45° with respect to the first direction. Coils are installed on the movable plate and the displacement portion, respectively. A horizontal scanning driving signal at a frequency of approximately 25 KHz having a sine waveform is input to the coil installed on the movable plate. A vertical scanning driving signal at a frequency of approximately 60 Hz having a saw-tooth waveform is input to the coil installed on the displacement portion. Accordingly, the movable plate is operated with respect to the displacement portion to correspond to the horizontal scanning driving signal. The displacement portion is operated with respect to the support portion to correspond to the vertical scanning driving signal.
JP-A-2005-250077 discloses an optical scanner including torsion bar springs in one direction. By doing so, in the optical scanner, a first movable plate is oscillatably supported by a pair of the torsion bar springs. One torsion bar spring portion is fixed to a support body. The other torsion bar spring portion is connected to a second movable plate. A coil is installed on the second movable plate and a magnetic field acts on the coil, and accordingly the second movable plate is oscillated. The first movable plate oscillates by oscillation of the second movable plate. The second movable plate has a damper structure. A Q value of the optical scanner is decreased by the damper structure. This damper structure is not a mechanism for suppressing mutual effects of the two movable plates.
A miniaturized optical scanner is desirable in order to use the optical scanner in a portable device. When miniaturizing the optical scanner disclosed in JP-A-2009-75587, it is also necessary to miniaturize the displacement portion. The coil installed on the displacement portion receives an electromagnetic wave output by the coil installed on the movable plate. Accordingly, the displacement portion to be only operated corresponding to the vertical scanning driving signal is operated with an influence of the horizontal scanning driving signal. In addition, the displacement portion is easily oscillated with an influence of the oscillation of the movable plate. When miniaturizing the displacement portion, an inertia moment of the displacement portion also decreases, and accordingly the displacement portion is easily affected by the horizontal scanning driving signal. As a result, the movable plate is operated with an oscillation component which is unnecessary for the vertical scanning. Therefore, an optical scanner having an improved vibration performance so that the horizontal scanning hardly affects the vertical scanning even with the miniaturized optical scanner, has been desired.